Production of pulp from highly resinous woods



Patented Dec. 5, 1939 PRODUCTION OF PULP FROM HIGHLY. RESINOUS WOODS Kurt Schwabe, Kriebstein, Post Waldhelm in Saxony, Germany, assignor to the firm oi Kiibler 8t Niethammer, Kriebstein, Post Waldheim in Saxony, Germany, and Chemische Fabrlk CoswigAnhalt, G. m. b. 11., Coswig in Anhalt, Germany No Drawing. Application September 22, 1937, Serial No. 185,227. In Germany June 28, 1937 1 Claim.

This invention relates to a process of producing mechanical wood pulp from woods rich in resin, particularly pine-wood.

During the grinding of woods rich in resin and 5 the further use of the wood pulp produced therefrom difilculties arise due to the sticking oi. the resin to machine parts, screens and felts. It has been attempted to overcome these troubles by using well seasoned wood in which the resin has solidified and forms a crystalline non-adhesive mass, but even in this case the old difilculties will ,appear again when hot grinding takes place. Cold grinding, on the other hand, involves disadvantages with respect to pulp quality and outll! put. It has further been tried to saponify the resin by the addition of alkalies, particularly soda, and thus render it harm'less. This process is, however, open to the objection that the stufl water has a strong tendency to foam, that at the slightest excess of alkali the pulp will be considerably discolored and that by the addition of substances lowering the pH value, such as bleaching agents like sodium bisulfite, precipita-.

tion of the resin may occur and bring back again the troubles it was intended to eliminate.

It has been found that the resin even of young highly resinous woods, particularly pine-wood, can be rendered harmless by being converted into the dimcultly soluble non-adhesive barium salt.

80 For this purpose, during or after the grinding operation water soluble barium compounds in solid or liquid form, preferably barium hydroxide, are added to the wood or pulp water, the quantities of hydrate to be added depending upon the 88 kind and age of the wood and fluctuating between 0.1 and 1 kg. per cubic meter wood. The grinding temperature should preferably not fall below 50 C. to insure the formation of barium salt without any trouble. A large excess of barium hydroxide will cause yellowing of the pulp, but it has been ascertained that no discoloration will occur if a pH value of '7 is not overstepped. The addition of barium hydroxide is therefore preferably kept within such limits that the alkaline region is not touched. The resinate of barium is a difllcultly soluble kaolin-like substance which to a large extent remains in the pulp as filler.

When acids are added, it does not change again and re-form free resin and thus becomes permanently harmless. Should the wood to be groundcomprise highly resinous branches, etc., it is advisable to add known dispersion agents,

for better distribution and conversion of the resin together with the barium hydroxide, 2% to 3% The application of the process described makes it possible to grind highly resinous woods, particularly pine-wood, without the least diillculty and to work the pulp obtained into paper. Furthermore, the devices used for working the wood pulp, especially the paper making machines, will not be soiled, and the paper produced from pulp of highly resinous woods will be fully equal in every respect to pape made from spruce pulp.

Instead of barium 'uble barium compounds and mixtures of such compounds can be used which are partly simpler to produce or disclose certain advantages in use. For example, barium oxide in solid form may be added to the wood pulp, or the resin can be eliminated by first saponifying it in known manner with alkalies, such as soda lye or soda, and then adding water soluble barium salts which lead to the separation of the barium salt of the resin acids. When for instance pine-wood is to be ground, one proceeds byilrst adding to the pulp, preferably directly at the grinder, the quantity of soda or soda lye required for the saponiflcation of the resin and then, possibly beforethe sorting of the pulp, enough barium chloride to insure complete conversion of the sodium salt of the resin into the barium salt. The barium chloride as well as the alkalies are preferably added in the form of'solutions.

, Instead of barium chloride, barium nitrate or any other water soluble barium salt may be added to the pulp after saponification of the resin by means of alkalies.

The resin can further be advantageously eliminated by adding to the pulp mixtures of water soluble barium compounds, such as a solution of barium hydroxide and barium chloride, in which case the barium hydroxide will take care of saponiflcation whilst precipitation of the resin is brought about by both compounds.

The resin can be eliminated also by adding to the pulp water soluble barium salts without previously saponifying the resin with the aid of alkalies, though in this instance it is advisable to add a dispersion agent simultaneously with or prior to the addition of the barium salts. Sulflte waste liquor may for instance be dropped on the resinous wood in the grinding outfit, whereupon after the grinding station a quantity of preferably dissolved barium chloride sufficient for precipitation is added to the pulp. 1 to 2 kg. of barium chloride per cubic meter of resinous wood will generally be enough. This method, too, insures ydroxide other'water solcomplete elimination of all troubles due to resin in the production and working 01' pulp irom highly resinous woods.

It is further possible to attain the object of the invention by an addition of barium carbonate which iorms water soluble salts with the acids present in the pulp.

Since the pulp water during the production of mechanical wood pulp is usually acid, with a pH value between 4 and 5, and this hydrogen ion concentration is chiefly produced by organic acids, particularly formic acid and acetic acid, soluble barium salts can be produced also within the pulp itself if barium carbonate is added to the water. It for instance during the grinding of pine-wood 2 to 3 kg. barium carbonate are added to the pulp water stream which should be as hot as possible, the acids mentioned above will bring about the formation of soluble barium salts which on their part eflect precipitation of the resin. It is advisable to add a dispersion agent.

I claim:

A process oi grinding wood pulp from highly resinous woods, consisting in adding to the pulp during the grinding operation barium hydroxide precipitating out the resin as insoluble barium resin soap and limiting the addition in order that the pulp water does not exceed a pH value of 'I. 

